In electronic vehicle systems such as electronic stability programs (ESP) for regulating driveability in the extreme range from the standpoint of driving dynamics, or in electronically regulated brake systems (EBS) for commercial vehicles, a value is generally needed for the mass of the vehicle. Since as a rule, no sensors are present for ascertaining the mass, the vehicle mass must be calculated or estimated by suitable algorithms.
German Published Patent Application No. 42 28 413 describes a method for determining the vehicle mass, in which two longitudinal vehicle accelerations at at least two different points of time and the propulsive powers existing at these points of time are measured. The vehicle mass is then determined from the difference between the propulsive powers and the difference between the longitudinal accelerations.
According to German Published Patent Application No. 198 02 630, to determine the vehicle mass, the propulsive power and the corresponding longitudinal vehicle acceleration are measured at points of time continually following each other with constant time intervals.
U.S. Pat. No. 6,347,269 describes ascertaining the vehicle mass on the basis of the propulsive powers, the running resistances and the vehicle acceleration, the influence of the roadway inclination being eliminated by a high-pass filter.
According to PCT International Published Patent Application No. WO 00/11439, to ascertain the vehicle mass, at least two time-staggered measurements are determined, including one tractive-force variable and one movement variable of the vehicle, one of the two measurements being carried out during a phase free of tractive force, and the other during a tractive-force phase.
In German Published Patent Application No. 101 44 699, a method is described which is based on the equilibrium relationship or ratio between the motive or driving force on one hand, and the accelerative force and the climbing resistance. This equilibrium relationship reads:F=m·(a+g·sin α)  (1)where
F=motive force
a=time derivation of the longitudinal vehicle velocity
α=gradient angle of the roadway
g=gravitational acceleration
m=vehicle mass
In equation (1), the accelerative force is represented by the product m•a, and the climbing resistance by the product m·g·sin α. To calculate mass m of the vehicle, equation (1) is therefore solved for m, and the instantaneous values for F, a and α are determined from measured quantities. Since gradient angle α of the roadway being traveled at any one time is not known, as a rule it is estimated with the aid of a computer during coupling phases or during phases without or with very low motive force, or is disregarded altogether. When using converter clutches or powershift transmissions, however, such freewheeling phases are no longer available, so that a sufficiently accurate estimation of the vehicle mass may be difficult.